Field of the Invention
The present invention relates to a heat energy recovery device for recovering exhaust heat.
Description of the Related Art
As a device for recovering heat energy from geothermal water and the like, a heat energy recovery device has been conventionally known, and a binary generator is a typical example of such device.
An example of the binary generator includes a power generator described in JP 2014-047636 A (hereinafter referred to as Patent Document 1). The power generator comprises a circulation flow passage where an evaporator, a super heater, an expander, an oil separation unit, a condenser, and a pump are sequentially connected in this order to form a closed circuit. Between the super heater and the oil separation unit, a bypass channel is provided for leading lubricant accumulated in the super heater to the oil separation unit, and the bypass channel includes a bypass valve. A temperature sensor for detecting the temperature of a working medium is provided both on the upstream and downstream sides of the super heater in the circulation flow passage. Further provided is a control means that calculates a heat exchange quantity in the super heater based on the difference in detection values of both temperature sensors (temperature difference), and opens the bypass valve at a point of time when the heat exchange quantity falls below a threshold.
In this power generator, the bypass valve is configured to open at a point of time when the heat exchange quantity in the super heater falls below the threshold, thus the lubricant in the super heater can be removed through the bypass valve. Having such configuration can suppress a decrease in efficiency of heat exchange in the super heater caused by the lubricant accumulated in the super heater.
However, in the power generator of Patent Document 1, the bypass valve is controlled based on the heat exchange quantity calculated from the detection values of the temperature sensors, thus the bypass valve is not always opened when the lubricant is accumulated in the super heater.
Further, if a heat quantity of a heat medium supplied to the evaporator and the super heater is insufficient or a circulation rate of a working medium is increased, the working medium in a liquid-phase and oil sometimes form a liquid layer in the super heater. When the lubricant is recovered by the method disclosed in Patent Document 1 in a binary generator that uses lubricant having a smaller specific gravity than the working medium, since a layer of the working medium in a liquid-phase is formed under a layer of the lubricant, the working medium layer is preferentially recovered to the oil separation unit, thus the amount of the working medium, which does not contribute to power generation, increases. As the result, the efficiency of power generation is decreased.
An object of the present invention is to provide a heat energy recovery device capable of properly operating under an environment in which a heat input quantity of a heat medium and a circulation rate of a working medium fluctuate.